Conventionally, a one-way clutch is employed in an automatic transmission. Japanese Patent Laying-Open No. 2-129454 discloses a one-way clutch lubricating device that is capable of forcedly lubricating a one-way clutch. The one-way clutch lubricating device lubricates a one-way clutch in an automatic transmission, which includes a case support wall inwardly extending from an inner peripheral surface of a case, the one-way clutch arranged adjacent to the case support wall, and a cylindrical member fitted to both an inner peripheral surface of an inner race of the one-way clutch and the inner peripheral surface of the case support wall, for rotatably supporting on its inner peripheral side a rotary member. Splines are formed on an outer peripheral surface of the cylindrical member so that a first spline coupling portion is formed relative to the inner peripheral surface of the case support wall and a second spline coupling portion is formed relative to the inner peripheral surface of the inner race. A lubricant oil supply hole opening to the first spline coupling portion is formed on the case support wall. An oil hole opening to the second spline coupling portion penetrating the inner race in a radial direction is formed in the inner race. At each position outside the opening in the first spline coupling portion, outside the opening in the second spline coupling portion, and between the case support wall and the inner race side surface, a seal portion is provided. A lubricant oil path is formed from the lubricant oil supply hole via the first and second spline coupling portions, and the oil hole, to a slide portion of the one-way clutch.
According to the one-way clutch lubricating device disclosed in the publication, the lubricant oil from the lubricant oil supply hole is supplied via the first spline between the inner peripheral surface of the case support wall and the outer peripheral surface of the cylindrical member, the second spline between the inner surface of the inner race of the one-way clutch and the outer peripheral surface of the cylindrical member, and an oil hole penetrating the inner race in the radial direction, to the slide portion of the one-way clutch. That is, a lubricant oil path for lubricating the one-way clutch is formed by the lubricant oil supply hole, the first and second splines, and the oil hole. Here, the lubricant oil path is sealed by the seal portions, and therefore the lubricant oil would not leak somewhere in the lubricant oil path. Accordingly, the lubricant oil supplied from the lubricant oil supply hole is forcedly supplied to the slide portion of the one-way clutch, without depending on centrifugal force or the like. Thus, the one-way clutch is always surely lubricated by a sufficient amount of lubricant oil, and the durability and reliability of the one-way clutch can largely be improved.
Some one-way clutches employed in an automatic transmission are configured to limit rotation of the outer race and the inner race relative to each other (so that an engaged state is attained) when driving in first gear (when running by the driving force of the vehicle), and to permit the rotation (to attain a disengaged state) otherwise (when running not by the driving force of the vehicle, such as when coasting). This is to suppress deterioration of the drivability caused by an engine brake while driving in first gear. Meanwhile, when a vehicle runs on an undulating road, for example, as the vehicle vibrates upward and downward, the wheels may repeatedly leave and touch the road surface. In such a case, the one-way clutch repeatedly permits and limits rotation of the outer race and the inner race relative to each other. This may cause popping (i.e., a sprag, a locking element, a roller and the like constituting the one-way clutch greatly vibrate and move violently) and the one-way clutch may be damaged. The one-way clutch may also be damaged if it abruptly transits from the state where the rotation of outer race and the inner race relative to each other is permitted to the state where the rotation is limited. However, the one-way clutch lubricating device according to Japanese Patent Laying-Open No. 2-129454 is not directed to suppress the damage of the one-way clutch in such a situation.